2. Xavier Bonnin and Davide Aguglia
A Hybrid Bouncer System for Highly Repeatable and Precise Klystron Modulators
Xavier Bonnin and Davide Aguglia
CERN – European Organization for Nuclear Research, Technology department, Electrical Power Converter Group
PPC 2017

3. Context: Compact Linear Collider (CLIC)
Parameter
Value
Unit
Nb of klystrons
1300
Voltage
180 kV
Current
160 A
Pulse length
140 µs
Rep. Rate 50 Hz
Stability
0.85 %
Repeatability 10
ppm
PPC 2017
Evaluation of a Hybrid Bouncer System for High Precision Klystron Modulators

4. Context: Compact Linear Collider (CLIC)
Parameter
Value
Unit
Nb of klystrons
1080
Voltage
180 kV
Current
160 A
Pulse length
148 µs
Rep. Rate 50 Hz
Stability
0.85 %
Repeatability 10
ppm
Large number of modulators => Reliability
Capacitor discharge based topology
High level of constraint on the precision
Compensation techniques are needed (bouncer circuits)
PPC 2017
Evaluation of a Hybrid Bouncer System for High Precision Klystron Modulators

5. Capacitor discharge based modulator
Bouncer circuit:
Goal: compensating the cap. bank voltage droop
Variety of technical solutions
Active switch(es)
Linear mode / switching mode / both
Passive resonant bouncer topologies
PPC 2017
Evaluation of a Hybrid Bouncer System for High Precision Klystron Modulators

6. Bouncer circuits examples
Corr
Ripple
Flex.
Robust
Eff
Linear ++ No + -
PPC 2017
Evaluation of a Hybrid Bouncer System for High Precision Klystron Modulators

7. Bouncer circuits examples
Corr
Ripple
Flex.
Robust
Eff
Linear ++ No + -
Switching
Yes
PPC 2017
Evaluation of a Hybrid Bouncer System for High Precision Klystron Modulators

8. Bouncer circuits examples
Corr
Ripple
Flex.
Robust
Eff
Linear ++ No + -
Switching
Yes
Corr
Ripple
Flex.
Robust
Eff
Linear ++ No + -
Switching
Yes
Hybrid
Passive
PPC 2017
Evaluation of a Hybrid Bouncer System for High Precision Klystron Modulators

9. Passive bouncer with linear switches
Requirements:
Vb < 0 or >0
ic < 0 or >0
=> 4-Q topology is needed
PPC 2017
Evaluation of a Hybrid Bouncer System for High Precision Klystron Modulators

10. Passive bouncer with linear switches
Requirements:
Vb1 > 0
ic < 0 or >0
=> 2-Q topology is needed
Other solution
2 switches in linear mode
Additionnal grounded power supply
PPC 2017
Evaluation of a Hybrid Bouncer System for High Precision Klystron Modulators

11. Passive bouncer with linear switches
Other solution
PPC 2017
Evaluation of a Hybrid Bouncer System for High Precision Klystron Modulators

12. Designing procedure Linear analysis:
Real Time compensation by the linear circuit
« Feedforward » compensation by the passive bouncer
PPC 2017
Evaluation of a Hybrid Bouncer System for High Precision Klystron Modulators

13. Optimize this term in order to minimize the pulse error
Designing procedure
Linear analysis:
Real Time compensation by the linear circuit
« Feedforward » compensation by the passive bouncer
Optimize this term in order to minimize the pulse error
PPC 2017
Evaluation of a Hybrid Bouncer System for High Precision Klystron Modulators

14. Optimize this term in order to minimize the pulse error
Designing procedure
Linear analysis:
Real Time compensation by the linear circuit
« Feedforward » compensation by the passive bouncer
Optimize this term in order to minimize the pulse error
PPC 2017
Evaluation of a Hybrid Bouncer System for High Precision Klystron Modulators

15. Optimize this term in order to minimize the pulse error
Designing procedure
Linear analysis:
Real Time compensation by the linear circuit
« Feedforward » compensation by the passive bouncer
Optimize this term in order to minimize the pulse error
New set of components and initial values
PPC 2017
Evaluation of a Hybrid Bouncer System for High Precision Klystron Modulators

16. Designing procedure Parameters: Components: Cb, L, Ltransfo
Initial conditions: Vin0, iL0 and Vb0
Constraints (equality):
Energy conservation in the bouncer (=steady state)
Sensitivity analysis (normalized function):
1% of error 100% deviation
10% of error  60% deviation
PPC 2017
Evaluation of a Hybrid Bouncer System for High Precision Klystron Modulators

17. Designing procedure Linear analysis:
Real Time compensation by the linear circuit
« Feedforward » compensation by the passive bouncer
PPC 2017
Evaluation of a Hybrid Bouncer System for High Precision Klystron Modulators

18. Designing procedure Linear analysis: LF compensator HF compensator
Real Time compensation by the linear circuit
« Feedforward » compensation by the passive bouncer
LF compensator
HF compensator
PPC 2017
Evaluation of a Hybrid Bouncer System for High Precision Klystron Modulators

19. Performances RMS error: 1500ppm Losses: 0.9% of Wpulse
Simulation results
PPC 2017
Evaluation of a Hybrid Bouncer System for High Precision Klystron Modulators

20. Monte Carlo simulation results
Performances
Sensitivity analysis:
500 runs
Parameters are randomly chosen in a +/-10% range around the optimal solution (bouncer components only)
Impact on precision and losses ?
Worst accuracy: 2600ppm
With only passive bouncer: 9700ppm
Highest losses: 1.3% of Wpulse
With only linear ballast: >5% of Wpulse
Monte Carlo simulation results
PPC 2017
Evaluation of a Hybrid Bouncer System for High Precision Klystron Modulators

21. Experimental set up
PPC 2017
Evaluation of a Hybrid Bouncer System for High Precision Klystron Modulators

22. Conclusion
Capacitor discharge based modulators need a compensation circuit (bouncer)
The presented topology aims at merging the advantages of a passive bouncer and an active linear stage
Acceptable level of losses
Fairly simple topology and control strategy
High bandwidth (linear)
Compensation of spread thank to a high bandwidth feedback control
PPC 2017
Evaluation of a Hybrid Bouncer System for High Precision Klystron Modulators